Currently suffering around 60 of these per hour:
{ "_index": "logstash-2015.06.29", "_type": "hhvm", "_id": "rOLcen60QZ6gFKCtfvhjBQ", "_score": null, "_source": { "message": "Fatal error: Call to undefined method SearchResultSet::addInterwikiResults() in /srv/mediawiki/php-1.26wmf11/extensions/CirrusSearch/includes/CirrusSearch.php on line 159", "@version": "1", "@timestamp": "2015-06-29T12:12:01.000Z", "type": "hhvm", "host": "mw1145", "priority": 11, "timestamp": "Jun 29 12:12:01", "logsource": "mw1145", "program": "hhvm", "severity": 3, "facility": 1, "facility_label": "user-level", "severity_label": "Error", "level": "Fatal", "tags": [ "syslog", "es", "normalized_message_untrimmed" ], "normalized_message": "Fatal error: Call to undefined method SearchResultSet::addInterwikiResults() in /srv/mediawiki/php-1.26wmf11/extensions/CirrusSearch/includes/CirrusSearch.php on line 159" }, "sort": [ 1435579921000 ] }